When is off-road not really off-road? When you're 550 feet down a salt mine, that's when. We didn't arrive here by accident, mind, for this is the location of the Mercedes GLA launch. And it's perhaps the most unusual place we've ever been in a car.

Mercedes-Benz is marketing the new GLA-Class under the tag line "capable on-road, capable off-road" and the salt mine at Winsford in Cheshire really takes the biscuit for supposed off-road locations. Yet the location proved precious little of the car's off-road ability, because the salt that comes from this place is what gets sprinkled on the roads in winter to keep us all moving.

Regardless, this underworld of fun was a playground for the GLA - a compact SUV that's based on the same platform as the hatchback A-Class - with us sat behind the wheel of the 200 CDi model. This lower-powered, front-wheel drive version from the series is the GLA that many people will actually buy with no pretention of traversing anything more difficult than their driveway.

That it'll be next to useless off-road doesn't stop the GLA from being quite an appealing proposition though. And it's a car that - in the real world - sometimes makes more sense than its sister car, the A-Class. That might sound surprising, especially when you consider that most people approach cars like the GLA with a degree of scepticism. Cars like this are niche, models designed to be the acceptable new face of the breed: compact, less-in-your-face, but with some of the greater traction advantages and higher driving position that people love about full-sized SUVs.

Yet the GLA stretches this idea to its extreme. It's less an SUV, more a high car - a scant 6cm taller than the A-Class in fact. And as already noted, in our tested two-wheel drive format, it's unlikely to get you far off-road. So what's the point in a high-riding, body-clad A-Class?

It's more than just a jacked up A-Class for a start. It might look similar, but the body is different. And then there's the drive: it's much more relaxed than the sportily set-up A-Class. The ride is a good deal more compliant and gentle whereas the A-Class is stiff.

And the good news for those on a budget or looking at their company car tax liability is that the lowest-spec 200 CDi we drove is possibly the sweetspot of the range. We drove the 220CDi '4matic' (Merc-speak for four-wheel drive) briefly, and the lower-powered car's engine seemed quieter, while still having enough oomph to complete overtakes without heart-stopping amounts of time on the wrong side of the road. So if you're not in a rush and want your passengers to arrive without revisiting what they had for breakfast, this could be the small Mercedes of choice.

The other quality the GLA has over the A-Class is space. It's not only slightly higher, but 12cm longer than the smallest Merc, so your rear passengers will thank you. There's also a whopping 481 litres of boot space in the GLA, which is more than some bigger SUVs.

In short, you get most of the good bits of the A-Class, with less of the bad. The cabin in the GLA is, frankly, a lovely place to sit. There's the same one-piece seats from the A-Class which hold you snug and in our car's AMG-Line trim were part finished in leather, further set off by some natty red stitching. That's mirrored on the dashboard - again, the same design you'll find in the A-Class - that features lovely electro-chrome plated "bullseye" airvents and Merc's familiar COMAND interface.

For clarity and ease of use this system - controlled by a small knob and buttons on the centre tunnel - is second only to BMW's iDrive system. Just the craggy graphics on the Merc's main screen and the ridiculously big bezel that surrounds the display - probably to highlight that you've not spent extra money on the larger-screen version - spoil things. Other than that, only the low set climate controls, and our continued ability to accidentally activate the cruise control or speed limiter via the Merc's secondary stalk - which is hidden behind the steering wheel, just below the indicator wand - annoyed us.

The GLA starts at around £25,800. That sounds a lot, yet it's cheap for a Merc and when you consider a decent-spec Volkswagen Golf is over £20k these days. So it starts to look half-reasonable value. On top of that is a decent standard kit spec including 18-inch alloys, DAB radio, the 5.8-inch display, cruise control and a collision-prevention assist system all as standard.

Out on the road, trying to drive a diesel soft-roader like your hair is on fire is a remarkably stupid exploit. But one most car journalists nonetheless partake in. But the GLA remains as refined as you'd expect at a motorway cruise from a car with the three-pointed start on the front. And while the response of the controls is a little soft and a times sluggish - the manual gear change is long throw - the GLA can be hustled with some conviction on narrow country roads because it's still a compact thing and body control is pretty good. Thrashing it on the road, we still got close to 40mpg too, so in the real world you might be knocking on the door of 50mpg.

It's all too easy to be cynical about the launch of what is ostensibly a niche product, but the Mercedes GLA deserves to become a regular site on our roads. The larger-than-A-Class body allows the styling to breathe just that little bit better, too. Spec it in a colour like red with the AMG wheels and it looks pretty darn good. The lower-body cladding and slightly pumped-up ride height seem to make sense in the cut and thrust of modern driving, plus you get most of the good bits of the A-class and with less of the bad.

The Mercedes GLA is less gawky than a BMW X1, less dorky than Mercedes' own B-Class and usefully more compact than an Audi Q3. And while the A-Class will doubtless appeal more to people after that young and cool image, for those looking for a compact, practical Merc the GLA is the smarter buy.

Although it won't cut the mustard off-road unless you happen to define off-road as down a salt mine, for most that won't matter. What will is that there's a practical, appealing and semi-affordable car with a three-pointed star on the front that you can buy with your head, not just your heart.